This invention relates to wharves, and more particularly to quays for conveniently loading and unloading ships.
There are several methods of constructing wharves. One method is to drive piles into the earth along or adjacent the shore of a navigable body of water. A platform is then constructed across the top of the piles. A channel is dredged along the wharf to allow a fully-loaded ship to tie up at the wharf without touching the bottom when the water is at its lowest level.
The wharf must be capable of supporting heavy loads of cargo and equipment encountered in loading and unloading a ship. The wharf also must resist the impacts of the vessels while berthing against the wharf. Consequently, the structural components of the wharf must be massive and sturdy. Piles individually are not massive and sturdy, but by adding bracing between piles, a reasonably rigid structure can be provided. This method of construction is slow and expensive.
Another disadvantage is that in cold climates, there is the danger of ice pressure and friction on the piles and bracing. This problem is aggravated when the water level rises and falls due to the effects of tide. In some areas of the Northern Hemisphere, the tide may rise and fall as much as 50 feet.
One alternative is to construct a solid quay structure adjacent the shore by sinking large reinforced concrete caissons in a row along the shore, and ballasting the caissons with fill. The area between the caissons and the shore is then back filled to the level of the top of the caisson. This method of wharf construction is a good one because of the large mass of the structure. However, the caissons must be partially precast in a dry area, and then floated and towed to the site where casting resumes up to completion. Furthermore, it is necessary to prepare a foundation underwater and to sink the caissons at the proper place on the foundation. All of these operations are very expensive.
Other alternatives for wharf construction use steel sheet piling either to constitute a curtain with anchorages containing the backfill for the quay platform, or form a sequence of jointed cells to be filled in order to obtain a gravity wall at the back of which the platform is backfilled. These alternatives require large amounts of costly steel and are often subject to incidental rupture of the tie-rods and anchorages, or to unfastening of the steel sheet file locks, particularly near the bottom imbedded in the foundation soil.